Nonaging flat silicon steel strip and method of producing the same



Patented 4, 1938 PATENT OFFICE NONAGING FLAT SILICON STEEL STRIP AND METHOD' OF PRODUCING THE SAME Charles A. samba, Brackenridge, Pa, assignor to'Alleiheny Steel Company, a corporation of Penmy yania No Drawing.

14 claim. My present invention relates to a method of annealing cold rolled silicon steel strip to make it a flat and non-aging.

The general practice has been to box anneal the finished cold rolled silicon steel strip at temperatures between 1400 and 2000 F. in coils in coils unavoidably takes the"set of the coil and such strip will not thereafter lie flat so that punchings 'or laminations made from coils annealed in this manner will be curved or non fiat, thus having a low space factor which makes it difficult and sometimes impossible to get the 1 proper weight of punchings or laminations into a core, and even when the prescribed weight can be obtained considerable strain is introduced into the punchings themselves, when thecores are tightened, which adversely afiectsthe magnetic 20. qualities. Again, finished strip which has been annealed continuously in strip form wherein the strip is'subjected to the above annealing temperatures for a comparatively short time and cooled at a fairly rapid rate may be flat, if the rolling and annealing operations have been conducted in a proper manner, but in such case the magnetic properties are not permanent. Consequently, in service, it has been found that the watt loss values will increase and the permeability will decrease and hence electrical apparatus built up from strip which has been so' treated will lose a considerable part of its efficiency. In addition, strip which has been so treated does not possess the well known nonaging properties which are characteristic of silicon steels and tests have shown that the watt loss values of steel so treated will increase from 25 to 50% when subjected to a temperature of 210 F. for 600 hours.

present invention to provide cold'rolled silicon steel strip which is not subject to the defects and disadvantages above outlined. and to provide a method of producing such silicon steel.

It is another object of the invention to provide cold rolled silicon steel strip which is characterized by having been subjected to a final'anneal of the character to be set forth whereby the indicated properties are'provid'ed in such steel s rip.

desired flat and non-aging properties.

It is accordingly one of.the objects of the A further object of theinvention is to subject- Application August 3', 1933, Serial No. 683,476

A still further object is to subject cold rolled silicon steel strip to a final anneal at 1000 to 1300 F. in the manner of a continuous anneal for a suitable length of time and suitably cooling the so annealed strip.

Other and further objects and advantages will be understood by those skilled in the handling of silicon steel or will be apparent or pointed out hereinafter.

In general, my present invention comprises the subjection of cold rolled silicon steel strip 10 which has been either box annealed or continuously annealed at a temperaturebetween 1400 and 2000 F. to a final annealing operation. My annealing operation is carried out at 1000 to 1300 preferably at about 1100 F., in the 1 manner of a continuous anneal for two to three minutes or for a length of time necessary to produce fiat and non-aging characteristics in the precise material undergoing treatment and then either rapidly or slowly cooling the same.

In orderthat my invention might be better understood it might be wellto describe the process by which the cold rolled silicon steel strip is produced. I The silicon steel ingots are heated to a suit-.- 25 able temperature and hot rolled into strip of as light a gauge as possible, that is, to a thick ness which is generally from .100 inch to .045 inch depending upon the silicon content, the kind and type of mill used, and the size of the 30 reducing rolls of the mill. The hot rolled strip is generally coiled and then annealed and pickled. The annealed and pickled strip is then reduced by cold rolling to the finished gauge. Usually the cold rolled strip is annealed before the fin 3 ished gauge is reached, in order to obtain the best magnetic properties. When the strip has been cold rolled to the finished gauge it is again coiled and the coil is then either box annealed at a temperature between 1400 to 2000" F. and 40 then slowly cooled, or the strip is uncoiled and continuously passed while flat through a furnace maintained at a temperature within the above temperature range. It is well known that strip which has been box annealed is non-aging, but will take the set of the coils, and when reeled from the coil will not be flat, and has the disadvantages which have already been pointed out.

It has been found that exceptionally good magnetic results may be obtained by the method of continuous annealing, but when the strip has been annealed in this manner it is aging, and when used in electrical apparatus the watt loss will increase and the'permeability decrease to such an 55 I have discovered that when silicon steel strip which has been her: annealed in coils within the temperature rouge given above is oncoiled and subjected to o continuous anneol while flat and at a temperature between 1000 to i300" F. and

then rapidly cooled such strip will be perfectly flat and will have magnetic properties equal to or slightly better their the box annealed strip, end that these values will he permanent. \Such strip can thenbe coiled without taking coll set.,- In other words, the strip when uncoilecl is flat and is non-aging. I have also found thot when silicon steel strip hos been continuously annealed within the temperature range oi 1400 to 2000. R, is then silhlecte'd'to a, continuous anneal between loco and 1300 F. for e, few minutes and rapidly cooled, it will be flat end managing, and have magnetic properties eouol to or slightly better than those cbtoioed in the first onheel. Such strip may also he coiled without taking e coll set.

The silicon steelol the present invention may contain'irom hoot to ohout coco, silicon and more broadly ted cootoins less thorn shoot 5% silicon; In the strip steel is intended for use in electrical oooorotos such so troosiomners, motors and other electricsll equipment making use of so=colled electrical steels cool is pcztlcu larly suitable ifor minorities or lorrimtioos for use therein.

' Since the Eliai oi invention is strip materiel produced hot and cold rolling procedures, the rcllings both hot cold ore corried on in the usuel simmer of producing strip material shot is, oil of the rolli carried on in one direction, the direction which the ingot is rolled.

Ecomyole .1?

Silicon steel strip containing 03% silicon and .0315 inch thick otter cox annealing in the regular mariner heel e, watt loss oi 3. .000 watts per pound et roots is and co cycles. lifter such box anneal the strip very wow Fond would not lie flat. The strip was then imcoiled and while fist woe annealed continuously at about 1100 F. for about two to three minutes and then rapidly cooled While still fist. when cooled otter this latter ermeal the strip was perfectly flat and did not take s set when recoile'd. Tests showed that it hook it watt loss oi only .0533 watt per pound at lililllil B end E30 cycles Alter coins; i hours 210 the value was about 1.01s watts goerooimd at will? B end to cycles indicating; thot cocaine Zimmclell Silicon steel strip oi o cl inch while fiat-at about 1100' for about two to three minutes and then rapidly cooled while still flat. After this anneal, the strip was perfectly flat and had a watt loss of 1.098 watts per pound at 10,000 B and 60 cycles. Alter aging 1150 hours at 210 F. the watt loss value was 1.108 watts per pound at 10,000 13 and 60 cycles indicating that no aging had resulted,

I have accordingly discovered that by subjectingsilicon steel strip of the character set forth al final to a final anneal, subsequent tcthe no anneal, under the conditions specifi E can produce flat non-aging cold rolled silicon steel strip of reduced watt loss and permanent magnetic properties; v

Such strip is far more valuable and has much greater utility and uniformity in electrical epparatus, than cold rolled silicon steel strip made by the present methods known tome.

It is understood that the foregoing is intended more in an illustrative manner than ihalimitatlve manner and that suitable additions, omissions, variations and substitutions may he made without departing from the spirit and scope of the in vention.

' What I claim 'as new and desire to secure by Letters Patent is:

1. In a method oi making magnetic-materiel in the term of silicon steel strip, the steps which consist in casting o, steel ingot loosing a silicon content of from about 5% to 0%, in reducing the ingot by hot rolling to o stoic oi intermediate gauge, in annealing the rolled strip, in. pickling the annealed strip, in cold rolling the pickled strip to fimhocl gauge, in annealing the strip or finished gauge rc iltfoicz o temperature range oi from 1400-2000" l t, in then cooling the strip,

, consist in casting e, steel ingot herring a silicon content of from about .5%, 5%, in reducing the ingot by hot rolling to at stri of intermediote gauge. in annealing the hot rolled strip, in pickling the annealed strip, iocold rolling the pickled strip to finished col ate, in o'onealing: the strip of finished gauge Within temperature rouge of from 1400-2000 El, in then cooling the strip, then in continuously canceling the strip while flat at a temperature of shoot ll00 F and then in coolingthe strip.

3. In a method of melting mccnetlc material in the form of silicon steel strip, the steps which consist in casting a steel ingot having a silicon content of from about 5% to 5%, in reducing the ingot by hot rolling to a, strip of intermediate gauge, in pickling the strip, in cold rolling the pickled strip to finished gouge, in box anneolioc the strip of finished cause o temperature range of from 1400-2000 K, in slowly cooling the strip, then in continuously annealing the strip while not at to temperature oi from hetween 1000 and l300- Fl. end-then cooling the strip while flat.

i. In a method of making; magnetic-materiel the form oi silicon steel strip, the steps which consist in casting o steel ingot-having a silicon content of from about 5% to 5%, in reducing the ingot by hot rolling to o strip of intermediategouoc, in cold rolling to finished gauge. in box annealing the strip of finished more within at temperature range oi from l-itMilOt 21"., in cooling the strip slowly, then in continuously annealing the strip while fiat at a temperature of about 1100 F., and then in cooling the strip while In a method of making magnetic material in the form of silicon steel strip, the steps which consist in casting a steel ingot having a silicon content or from about .5% to 5%. in reducing the ingot by hot rolling to a strip of intermediate gauge, in cold rolling to finished gauge, in anthe strip, and then in continuously annealing the strip while flat at a temperature of about 1100 I".

6. In a method of making magnetic material in the form of silicon steel strip, the steps which consist in casting a steel ingot having a silicon content of from about .5% to 5%, in reducing the ingot by hot rolling to-a strip of intermediate gauge, in cold rolling to finished gauge, in box annealing the strip of finished gauge within a temperature range of from 1400-2000" F., in 0001- ing the strip slowly, then in continuously annealing the strip while flat at a temperature of from 1000 to 1300 F., and then in rapidly cooling thestrip while flat.

'7. In a method oi making magnetic material in the form oi'.silicon steel strip, the steps which consist in eflecting a heavy reduction by cold work, heating the strip to a temperature of from about 1400 to about 2000" 1"., in cooling the strip, then subjecting the strip while fiat to a-continuous anneal of from about 1000' to about 1300' 1".,-

and then cooling the strip while flat. v

8. In a method of making magnetic material .in the form of silicon steel strip, the steps which consist in electing a heavy reduction by cold work, heating the strip to a temperature or from about 1400 to about 2000 1"., in then cooling the strip, then subjecting the strip while ilat to a 7 continuous anneal at about 1100 1., and then in cooling the strip while flat.-

9. In the art of making a coil of magnetic meterial'in the form of silicon steel strip which is non-aging and tree from-coil set, the steps which consist in reducing suitable silicon steel by hot and cold rolling operations to a strip '0! finalgauge, in then annealing such strip of final gauge within a temperature range of from 1400 to 2000 F., in cooling the strip, in continuously annealins the strip while fiat within a temperature range of from 1000 to 1309 E, in then cooling the strip while flat and then in coiling the same.

10. In the art of making a coil of magnetic material in the form oi-silicon steel strip which is non-aging'and tree from coil set. the steps which consist. inreducing suitable silicon steel ature range 01 irom 1000 to 1300 It,

strip. ealing the strip of finished gauge within a temperature range of from 1400-2000" It. in cooling ,nealed at a temperature by hot and cold rolling operations toa strip oil;

that gauge, in coiling the strip or final gauge, in box annealing the coiled strip, .in cooling the coiled strip, in uncoiling the strip. in continuously annealing the strip while fiat within in cooling the strip while flat and then in re-coilins the 11. In the artot making a coil of magnetic material in the form of silicon steel strip which is non-aging and free from coil set, the steps which consist in reducing suitable silicon-steel by hot and cold rolling operations to a strip of final gauge, in then annealing such strip of final gauge within a temperature range of from 1400 to 2000" F., in cooling thestrip, in continuouslyannealing the strip while flat at about 1100 F.,

in then cooling the strip while flat and then in.

coilingthe same.

12. Inthe art of making a coil' or magnetic material in the form of silicon steel strip which is non-aging and free from cell set, the steps which consist in reducing suitable silicon steel by hot and cold rolling operations to a strip 01' final gauge, in coiling the strip of final gauge, in box annealing the coiled strip, in cooling the coiled strip, in uncoiling the strip, incontinuously anhealing the strip while flat at aboutj1100 F., in cooling the strip while fiat and then in recoiling the strip. i

13. As a new article of manufacture, a coil of a tempermagnetic material in the form of cold rolled sili- I can steel strip having a silicon content between approximately -.5% and 5% which is non aging' and free from coil set and produced from a strip of silicon steel having a silicon content withinthe limits set forth which has been annealed at a temperature between approximately 1400 1"..and 2000 E, cooled, then subjected to a continuous anneal at a temperature of approximately 1100" I". and again cooled.

14. As a new article of manufacture, non-aging magnetic material in the form of silicon steel strip free from coll set and having a silicon content 

